The latest salvo in the breast-cancer screening war is due to be fired Thursday, as a major cancer charity launches a new campaign telling women to, essentially, ignore controversial research that suggests regular mammograms are of limited value, and can even do harm.

The continued tension over breast X-ray screening — other respected experts say it is time to at least question how widely mammograms are used — underlines one of the most extraordinary medical-science debates in recent memory, with signs the health-care world is deeply divided over a once-unquestioned early-detection program.

In the middle are women left confused by the conflicting views, and even some doctors struggling to make sense of the heated discourse.

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“As a surgeon and a scientist, I’ve found the resurrection of the debate … to be simultaneously frustrating, educational, and confusing,” Dr. David Gorski, a Wayne State University cancer surgeon, commented recently on his Science-based Medicine blog.

The Canadian Breast Cancer Foundation is scheduled to release a poll Thursday that suggests many Canadian women are also feeling frustrated about the issue. The Ipsos Reid survey suggests that almost 70% are confused by the conflicting information, and 42% say they don’t know whether the benefits of breast-cancer screening outweigh the risks.

Slightly more said they were questioning whether to undergo screening at all, according to the poll of 1,500 women.

In response, the foundation – Canada’s largest non-governmental funder of breast-cancer research– has set up a new Facebook page, My Breast My Test, designed to help women “get past the confusion and uncertainty about breast cancer screening.”

Although it is unclear whether women are, in fact, eschewing mammograms, the risk of that happening is serious, argued Sandra Palmaro, the foundation’s CEO.

“It would be tragic if even one women died because she decided not to be screened because she received incorrect information,” Ms. Palmaro said.

Mammograms are specially designed X-rays of the breast. The issue is not about using them to diagnose possible cancer when a lump or other symptom is detected; that application of the technology remains unchallenged. The debate concerns screening programs where seemingly healthy women undergo mammograms to find otherwise undetected cancers.

I can’t speak for anyone else. All I know is a mammogram saved my life

Brenda Stover, a Tillsonburg, Ont., woman slated to appear at a foundation news conference Thursday, said she is glad she underwent such a test in June, 2012. It found a stage-two tumour that even the surgeon could not find by manual examination, and is now in good health after surgery, chemotherapy, radiation and other treatment.

“I can’t speak for anyone else,” she said Wednesday. “All I know is a mammogram saved my life.”

Much of the controversy has centred on a large Canadian study, which began in 1980 and issued its third report this February. The randomized controlled trial assigned half the 90,000 subjects aged 40-59 to receive mammograms – or mammograms plus manual breast exams for those 50 and over – and half to a control group that received just breast examinations.

A quarter-century later, deaths from breast cancer were almost equal – 500 in the mammogram group and 505 in the control group, according to a paper in the British Medical Journal. The authors suggested also that about 20% of the mammography-identified cancers were instances of “over-diagnosis” – disease that is found and treated but that would not pose a danger to the woman’s life.

That study’s finding that mammography does nothing to reduce death from the cancer is at the outer edge of the debate. Yet other scientists – including influential medical advisory bodies in Canada, the U.S. and other countries – have suggested that the risk of false positives and over-diagnosis outweigh the life-saving benefits at least for women younger than 50.

Still, Ms. Palmaro suggested that the notion there is widespread debate among experts about the benefit of screening is largely a creation of lopsided news media reporting.

“It seems almost like the teams are equal when they are not, by any reach,” she said.

But Dr. Anthony Miller, lead author of the Canadian breast-cancer screening study, suggested his work is only part of a growing body of research asking questions about mammography.

“Things have been shifting,” he said. “Increasing numbers of people are recognizing that the data are not as good as has been promulgated …The risk-benefit equation needs to be reconsidered.”